Miniature switch



Jan. 8, 1957 NORTON I 2,777,037

MINIATURE SWITCH Filed Nov. 2, 1955 JAMES P. NORTON,

/NVNTOR ATTORNEY MINIATURE SWITCH James P. Norton, Los Angeles, Calif., assiguor to Hughes Aircraft Company, Culver City, Calif., a corporation of Delaware Application November 2, 1955, Serial No. 544,429

2 Claims. (Cl. 200--159) The present invention relates to. switches and more particularly to a miniature switch that is substantially without bounce at relatively high speeds.

A switch is merely a device used in electrical circuits for completing or interrupting. the circuit. When the switch is open, electrical signals applied to the input terminal of the switch are prevented from passing to its output terminal. Thus, the circuit is interrupted or open. On the other hand, when the switch is closed, signals applied to its input terminal are produced at its output terminal and the circuit is considered complete or closed.

Most of the miniature switches found in the prior art employ a cantilever type of spring element for closing and opening the switch, that is, for electrically connecting and disconnecting the input terminal to and from the output terminal. It has been found that switches using this type of spring element have a great tendency to bounce when the spring is operated at more than 1000 cycles per minute. More specifically, it has been found that a cantilever type of spring element has a natural resonance frequency and that, during the continuous or cyclical operation of the switch at relatively high speeds, the switch has an inherent tendency to oscillate at this resonance frequency. As a result, electrical signals applied to the input terminal of these prior art miniature switches While they are operated at relatively high speeds are produced at the output terminal containing undesirable transient oscillations.

It is therefore, an object of the present invention to provide a miniature switch having very little tendency to bounce when the switch is operated at relatively high speeds.

It is another object of the present invention to provide a miniature switch that faithfully reproduces electrical signals applied to the switch during high speed operation thereof.

It is a further object of the present invention to provide a miniature switch that substantially eliminates bounce during high speed operation by quickly dampening undesirable oscillations that may occur in the moving parts of the switch.

The present invention overcomes the bounce problem encountered in prior art switches by providing a switch that operates under conditions that tend to prevent oscillations from occurring and to quickly damped them once they have occurred. More particularly, the switch of the present invention includes a pair of leaf springs that are spiraled intermediate their centers and their ends to effectively increase the working length of the springs. As a result, when the springs are deflected, the stress in the springs can be maintained well below the elastic limit, thereby greatly improving the operation and life of the switch at high speeds. The bounce problem is also greatly alleviated in the switch of the present invention by providing a dampening device, such as a rubber pad, which at all times is in close contact with one of the springs and, thereby, helps to quickly reduce the amplitude and duration of oscillations that may arise. As an example,

2,777,037 Patented Jan. 8, 195.7

a miniature switch built in accordance with the present invention was tested and it was found that. such, a switch could be operated at 6500 or more cycles per minute with a good signal response.

The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages thereof, willbe better understood from the following description considered inconnection with the accompanying drawing in which an embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawing is for the purpose of illustration and description. only, and is not intended as a definition of the limits of the invention.

The figure shows a perspective view of a miniature switch according to the present invention, the case enclosing the switch being shown in phantom.

Referring now to the drawing, there is shown in the figure a miniature switch, according to the present invention, for making and breaking the electrical continuity between an input. terminal 10 and an output terminal 11. More specifically, the miniature switch. comprises a pair of springs 12 and 13, preferably leaf springs made of a resilient and current conductingmaterial, such as beryllium copper, one spring being positioned directly over the other as shown in the figure. Each spring is spi-raledintermediate its center and its ends, the ends of spring 12 being designated 14 and 15 and the ends of spring 13 being designated 16 and 17. It will be noted that the ends, such as 14, 15 of spring 12, extend in opposite directions away from the plane of the main body of the spring. However, this condition is not essential. Ends 14-17 are rigidly fixed in position by a frame or box 18 supporting the switch and shown in phantom, ends 14 and 16 being electrically connected through the box to terminals 10 and 11, respectively.

A push button, generally designated 20, is mounted on the center portion of spring 12 through an opening in the top side of box 18. The push button includes an upper portion 21 made of an insulating material and a lower portion 22 made of a current conducting material, the lower portion having a slot 23 through which spring 12 extends for mounting the push button. Lower portion 22 is soldered to spring 12, as indicated by the small circles in the slot, and is, therefore, at all times in electric-al contact with the spring. Furthermore, spring 12 and 13 are so disposed relative to each other that conduc'tive portion 22 is contiguous -to or, stated diiferently, in close proximity to spring 13. Thus, a slight displacement of push button 20 toward spring 13 would bring conductive portion 22 into electrical contact with spring 13. Push button 20 is protected by a cylindrical shaped guard 25. I

A rubber pad 24 is mounted between the center portion of spring 13 and the bottom side of box 18, as shown in the figure. The rubber pad is used as a dampener to prevent undesirable oscillations of the springs and to help return spring 13 to its original position when the displacement forces are removed from the push button 20, as will be described in greater detail below.

Considering now the operation, it will be assumed initially that push button 20 is in an undisplaced position and, therefore, that springs 12 and 13 are in an unconstrained, spaced position. Accordingly, lower portion 22 of the push button is separated from spring 13 so that the electrical continuity between input terminal 10, lower portion 22, spring 13 and output terminal 11 is broken. When push button 20 is depressed, lower portion 22 is brought into physical and, therefore, electrical contact with spring 13. As a result, electrical continuity is established between input terminal 10, spring 12, lower porarcane tion 22, spring 13 and output terminal 11. Thus, while push button 20 is depressed, electrical signals applied to input terminal 10 will be produced at output terminal 11.

When the force previously applied to push button 24) for depressing the button is removed, the resiliency of springs 12 and 13, aided by rubber pad 24, returns the push button to its free or undisplaced position. As a result, the gap or space between lower portion 22 and spring 13 is reopened, thereby causing the electrical continuity between the above-mentioned parts to be broken again.

It should be noted that additional rubber pads may be placed between the top side of box 18 and spring 12, thereby further to reduce the incidence and duration of oscillations in the springs.

Furthermore, although the present in ill has been shown and described as a single-pole, stri -throw type of switch, it will be immediately apparent la hose skilled in the art that other embodiments may constructed, such as a double-throw type of switch, /ithc-ut departing rfrorn the spirit and scope of the invention as set forth in the appended claims.

What is claimed as new is:

1. A miniature switch for completing and interrupting the electrical continuity between a pair of terminals, said switch comprising: a first spring having a spiral intermediate its center and ends, the ends being :(ed in position, one of said ends being electrically connected to one of the terminals; a second spring having a spiral intermediate its center and ends, the ends being fixed in position, one of said ends being electrically connected to the I 4 other of the terminals; a push button mounted on said first spring and at all times in electrical connection therewith, said push button being contiguous to said second spring and movable into electrical contact therewith; and a rubber pad pressing against said second spring for dampening out any oscillations of said springs that may occur during operation of the switch.

2. A miniature switch for electrically connecting and disconnecting first and second terminals, said switch comprising: first and second leaf springs lying in a plane, one spring being positioned directly over the other spring, said springs having spirals intermediate their centers and their ends, the ends being fixed in position, at least one end of said first spring being electrically connected to the first terminal and at least one end of said second spring being electrically connected to the second terminal; a push button mounted on said first leaf spring and at all times in electrical connection therewith, said push button being contiguous to said second leaf spring and movable into electrical Contact therewith; and means for cushioning at least one of said springs to prevent said springs from oscillating and to quickly dampen oscillations that may occur during operation of the switch.

References Cited in the file of this patent UNITED STATES PATENTS 580,092 7 Moore Apr. 6, 1897 859,278 Wright July 9, 1907 1,006,394 Morrell Oct. 17, 1911 

